1. Field of the Invention
The present invention relates to a lubricant applying system for a rolling bearing, in particular, an apparatus for applying a lubricant to the interior of a rolling bearing, and an apparatus for inspecting a lubricant applied condition of a rolling bearing adapted to inspect whether or not a lubricant is applied to the interior of the rolling bearing.
2. Description of the Related Art
FIG. 15 shows the construction-of a rolling bearing. In the figure, reference numeral 700 denotes a rolling bearing, which is constituted by an outer race 701, an inner race 702 and a crown-shaped retainer 704 provided between the races for retaining a plurality of ball-like rolling elements 703.
Known as a conventional method for applying a lubricant to the interior of thus rolling bearing 700 is describes an oil plating method for slightly applying a lubricant on a bearing raceway surface (Japanese Patent Unexamined Publication No. SHO 64-46011), a method including the steps of dipping the assembled rolling bearing 700 in a lubricant, picking up the rolling bearing 700 from the lubricant and removing the lubricant therefrom in a centrifugal fashion (Japanese Patent Unexamined Publication No. HEI 8-303467), or a method including the steps of dipping the rolling bearing 700 in a lubricant diluted with a solvent (petroleum benzine) and thereafter allowing the solvent to evaporate (Japanese Patent Unexamined Publication No. HEI 5-149343).
Widely adopted as a means for assembling the rolling bearing 700 to an apparatus is a method for adhering a radially inner surface of the inner race 702 to a shaft or for adhering a radially outer surface of the outer race 701 to a housing. In these methods, the adhering surfaces of the rolling bearing 700 are required to be dry (hereinafter, described as a first case).
In addition, in an apparatus such as a hard disk drive in which a high degree of cleanness is required in the interior thereof, the volume of lubricant component running out of or flying from the rolling bearing 700 needs to be as little as possible. This requires a flat portion as well as the radially inner and outer surface portions of the rolling bearing 700 to be sufficiently dry. Moreover, if there is some lubricant adhering to a sealing groove portion formed in the outer race 701 and the inner race 702, this adhering lubricant runs out of the sealing groove portion when a seal is inserted thereinto, and therefore this sealing groove portion also needs to be sufficiently dry (hereinafter, described as a second case).
Furthermore, a fiber constituent contained in grease as a lubricant is not too good to reduce and stabilize the torque of the rolling bearing, and therefore there are some rolling bearings 700 in which grease is required to be put on the retainer 704 in order to reduce and stabilize the torque thereof. In this case, when some of the lubricant required for lubrication in an initial stage (oil component in the grease runs out thereof soon after the initial stage and this oil component contributes to the lubrication of the rolling bearing) adheres to the portion where grease is put, the grease becomes easy to slide down over the retainer 704, and it moves and comes to adhere to rolling element raceway surfaces of the outer and inner races 701, 702 while the rolling bearing 700 is rotating. Therefore, the torque is increased and caused to vary. In order to prevent this, no lubricant has to adhere to the portion of the retainer 704 where grease is put (hereinafter, described as a third case).
In addition, there is a case where any combination out of the above three cases simultaneously constitutes a problem. In other words, a problem is caused by a combination of the first and second cases, the first and third cases, or the second and third cases. Moreover, there is a case where the first, second and third cases simultaneously constitute a problem.
Namely, it is important that no lubricant adheres to any portion in the interior of the rolling bearing 700 that does not really needs lubrication. What needs lubrication in the interior of the rolling bearing 700 are the rolling element raceway surfaces of the outer and inner races 701, 702 and the surface of the rolling elements 703.
In the aforesaid conventional example, however, it is not possible to apply a lubricant only to portions in the interior of the rolling bearing 700 which need lubrication and it is unavoidable that a relatively large volume of oil component adheres to portions in the interior of the rolling bearing 700 other than those that really need lubrication. In addition, in the above-described conventional example, it is very difficult to dry only the exterior of the rolling bearing 700 with a needed volume of lubricant being left in the interior thereof. Moreover, manual removal of oil component adhering to the exterior of the rolling bearing 700 causes an increase in costs.
Moreover, it becomes important to inspect whether or not a lubricant is injected into the interior of a rolling bearing through a total inspection for judgement of defective or non-defective. However, in the methods described in the aforesaid publications, only the process of applying the lubricant is described and none of the methods describes therein a process of inspecting a lubricant-applied condition of the rolling bearing after the lubricant is applied thereto. Thus, there is caused a problem that whether or not the lubricant is properly applied to the completed rolling bearing is unclear.